It is not specified whether charge is +1 or -1.
If charge is +1, then total no. of electrons is 110,and so is atomic number.
Mass No.=No. of neutrons+ Atomic Number (1)
=159+110=269
If Charge is -1, total no.of electrons= 108= atomic number
From (1)
Mass No.= 159+108=267
Hope It Helped :)
